Modern lightweight and durable articles require a variety of physical properties which frequently are not achievable with a monolithic material approach. Materials with variable properties, that is variation in a property among different levels or layers, over the depth of the article, are described in prior art. These include parts with graded properties, that is having in different levels, different porosities, compositions, grain sizes, filler amounts and/or hardness.
One approach to providing metallic articles graded according to one or more properties, that is multilayers with different properties in different layers, is by compaction of sintered powder. This method is disadvantageous because it incorporates impurities, provides limited shapes, is high energy requiring, and is not readily scalable.
It has been recognized that a better method for producing multilevel and or multilayered products comprising metallic material is by pulse electrodeposition. Detor et al. U.S. Patent Application Publication No. U.S. 2006/0272949 A1 teaches an electrodeposition process involving bipolar pulsing and selection and variation of Polarity Ratio to provide graded structures with different grain sizes and/or compositions in different grades solely in the deposition direction. Changing the Polarity Ratio involves changing amplitude and/or duration of negative portions of a pulse relative to positive portions. This method has the disadvantages that it is not applicable to pure metals, i.e., is only applicable to alloys, and that it is dependent for grading on changing Polarity Ratio, a parameter that is not directly supplied to the system. The employment of reverse pulses requires expensive power supplies and results in a significantly reduced plating efficiency as metal dissolution occurs during the reverse pulses.